Test away!
I bought my 13 year old nephew a potato gun for his birthday last year, didn't go over too well with the rest of the family. It was of the compressed air type, not the explosive charge type. I gave it a brief thought as a shotline launcher, but the BigShot is just too effective to try something more expensive and complicated.
I look forward to seeing your results. I don't think a half charge can provide the 'horsepower' to move that mass very far against gravity and frictional air resistance, but the pull of the trigger will tell.
I'm thinkin a hollow, bottom-end-sealed, aluminum tube with a golf ball as the projectile head. Heh heh.
Your line will slow things also, it's really fat, as far as a practical shotbag line. 'Course, yours is not a shotbag line, it's a shotgun line, so as far as experience goes, I really don't have a clue. 1.75 mm zing-it line, or braided 80 lb test fishing line, maybe. Just a guess.